1. Field of the Invention
The present invention is related to a wireless communication, and more particularly to a method of transmitting system information related to a point-to-multipoint service.
2. Related Art
Similarly to a conventional cell broadcast service (CBS), a point-to-multipoint service such as multimedia broadcast/multicast service (MBMS) simultaneously transmits a data packet in the same manner to a plurality of users. The CBS is a low-speed message-based service whereas the MBMS aims at high-speed multimedia data transmission. Further, the CBS is not based on an Internet protocol (IP) whereas the MBMS is based on IP multicast. If users satisfying a specific level exist in the same cell, necessary resources (or channels) transmitted to each user are shared so that a plurality of users can receive the same multimedia data. Therefore, the MBMS has an advantage in that radio resources can be more efficiently used and a multimedia service can be used at a low price from the perspective of the users.
The MBMS uses a common channel so that a plurality of user equipments (UEs) effectively receive data of one service. That is, regarding the data of one service, only one common channel is allocated instead of allocating a predetermined number of dedicated channels corresponding to the plurality of UEs which intend to receive the service in one cell. Since the plurality of UEs simultaneously receive the common channel, efficiency of radio resources increases.
There are many differences between MBMS and unicast service in terms of radio bearers, radio resources, scheduling parameters, transport channels, frame structures, etc. Therefore, system information needs to be separated between MBMS UEs and non-MBMS UEs because non-MBMS UEs doesn't always have to receive MBMS data. And notifying the changes of system information for MBMS and non-MBMS should be performed in different ways.